Tiny particles propel themselves upstream
Environment-sensing microbeads may one day deliver medicines
![human-made particle](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2015/05/ay_particle_upstream.jpg?fit=860%2C460&ssl=1)
AGAINST THE FLOW In a new experiment, micrometer-sized particles sensed their direction and propelled themselves upstream. Each particle (one shown in this micrograph) was made of a plastic sphere engulfing a hematite cube (colored red).
Stefano Sacanna